Field
The present disclosure relates to a washing machine, and more particularly to a tub, which is made by injection molding with a bearing housing inserted therein, and a washing machine having the same.
Discussion of the Related Art
In general, washing machines are apparatuses which perform washing, rinsing, and dehydration operations by rotating a drum or a pulsator using the driving force of a motor. Wash water is accommodated in a tub, and the drum is rotatably provided in the tub.
According to the operation methods of washing machines, the washing machines may be classified into an indirect-connection type washing machine, in which the driving force of a motor is transferred to a drum using a pulley or the like, and a direct-connection type washing machine in which the driving force of a motor mounted to a tub is directly transferred to a drum. In recent years, the direct-connection type washing machine has been increasingly utilized.
The structure of a direct-connection type drum washing machine will be briefly described with reference to FIG. 1.
A tub 2 is provided in a cabinet 1, and a drum 3 is rotatably provided in tub 2. A motor, which consists of a stator 6 and a rotor 5, is mounted to the rear wall portion of tub 2.
Rotor 5 surrounds stator 6, and is connected to a shaft 4. Shaft 4 is coupled to drum 3 through the rear wall portion of tub 2. Accordingly, the rotation of rotor 5 is directly transferred to drum 3 via shaft 4.
The rear wall portion of tub 2 is provided with a bearing housing for rotatably supporting shaft 4. The bearing housing may be mounted to tub 2, or may be integrally formed with tub 2 by insert-injection molding.
FIGS. 2 and 3 illustrate an example of a conventional tub 20 made by injection molding with a bearing housing 30 inserted therein. FIG. 2 illustrates an outer surface of a rear wall portion 21 of tub 20, and FIG. 3 illustrates an inner surface of the rear wall portion 21 of tub 20. A washing machine having such a tub is disclosed in PCT International Application No. PCT/KR2006/001622 (PCT International Publication No. WO2007/126167), which is a related patent.
The entire bearing housing 30 is substantially inserted in rear wall portion 21 of the tub, except for a central hub 31 thereof. That is, bearing housing 30 is not exposed to the outside, but is surrounded by tub. A shaft passes through the center of hub 31, and bearings are provided inside the hub.
Bearing housing 30 is arranged radially inward on the basis of line “A” shown in FIGS. 2 and 3. Accordingly, the inside of line “A” may be called an insert portion 22 in which the bearing housing is inserted in the tub. On the other hand, the outside of line “A” may be called a non-insert portion 23 in which the bearing housing is not inserted in the tub.
Bearing housing 30 includes a stator mounting portion in which concave portions 32 and convex portions 33 are formed in a repetitive pattern in a circumferential direction from the outside of hub 31 in the radial direction thereof. Accordingly, hub 31 and the stator mounting portion are integrally formed and inserted in the tub. FIG. 2 illustrates the state in which a bearing housing 30 having six concave portions 32 and six convex portions 33 is inserted in tub 20. Here, the stator mounting portion may correspond to the outer surface of rear wall portion 21 of the tub.
The non-insert portion 23 of tub 20 is formed to have the same pattern as insert portion 22. That is, concave portions 24 and convex portions 25 of the tub are formed similarly to concave portions 32 and convex portions 33 of bearing housing 30. Concave portions 24 and convex portions 25 are reversely shown as convex portions 24′ and concave portions 25′ on the inner surface of rear wall portion 21. That is, convex portions 24′ on the inner surface of the rear wall portion of the tub are shown as concave portions 24 on the outer surface of the rear wall portion. The same is true for respective convex/concave portions 25 and 25′.
The inner surface of rear wall portion 21 of the tub has a shape and a pattern which are identical or similar to those of the outer surface of rear wall portion 21 of the tub.
Accordingly, in rear wall portion 21 of the tub, concave portions 24 and 25′ and convex portions 25 and 24′ are formed in a repetitive pattern in the circumferential direction from the outside of hub 31 in the radial direction thereof. This pattern extends to the edge of rear wall portion 21 of the tub. In other words, the shape and pattern of the bearing housing, which is arranged inward from line “A”, are identically formed throughout rear wall portion 21 of the tub.
However, the tub has the following problems.
First, noise may increase due to concave portions 24 and 25′ and convex portions 25 and 24′ of rear wall portion 21 of the tub. Wash water accommodated in the tub is tumbled according to the rotation of the drum. Concave portions 24 and 25′ and convex portions 25 and 24′ act as obstacles to the tumbling of wash water. Particularly, concave portions 25′ on the inner surface of rear wall portion 21 of the tub act as resistance to wash water, thereby causing noise when the drum rotates.
Secondly, bearing housing 30 may protrude through rear wall portion 21 of the tub at line “A”, i.e. at the boundary between insert portion 22 and non-insert portion 23. For this reason, the position of the bearing housing is dislocated due to vibration, thereby entailing the risk of damage to the tub. In other words, the bearing housing may be inadequately coupled to the tub.
Thirdly, because insert portion 22 and non-insert portion 23 have the same pattern, the thickness of the tub may be increased. Particularly, the thickness of the tub may be unnecessarily increased at the edge of rear wall portion 21 of tub 20. For this reason, the weight of the tub and material costs are increased.
The exterior size of a conventional washing machine, i.e. the horizontal width of a cabinet, is mainly 24 or 27 inches. Due to this external size, the drum and the tub may have only a limited size, and thus the washing machine may have only a limited washing capacity of about 15 kg.
However, in recent years, the exterior size of the washing machine has enlarged to 29 or 30 inches, and thus the washing machine is enlarged to have a washing capacity of about 20 kg. Accordingly, the sizes of the drum and the tub, especially the diameters thereof are necessarily increased. Of course, the motor for driving the drum has an increased size, and the required torque of the motor is also increased.
For this reason, there is a need to improve the structure and the size of the conventional bearing housing in order to more securely fix the motor.